The development of the human body; a manual of human embryology . the foramenof Monro to the tip of the temporal lobe (Fig. 228, h). Itaffects the entire thickness of the pallial wall and conse-quently produces an elevation upon the inner surface, aprojection into the cavity of the ventricle which is knownas the hippocampus,whence the fissuremay be termed thehippocampal portion of thepallium which inter-venes between thisfissure and the chori-oidal forms what isknown as the dentategyrus. Toward the end ofthe third or the be-ginning of the fourthmonth two prolonga-tions arise from t
The development of the human body; a manual of human embryology . the foramenof Monro to the tip of the temporal lobe (Fig. 228, h). Itaffects the entire thickness of the pallial wall and conse-quently produces an elevation upon the inner surface, aprojection into the cavity of the ventricle which is knownas the hippocampus,whence the fissuremay be termed thehippocampal portion of thepallium which inter-venes between thisfissure and the chori-oidal forms what isknown as the dentategyrus. Toward the end ofthe third or the be-ginning of the fourthmonth two prolonga-tions arise from the fissure just where it turns to becontinued into the temporal lobe, and these, extendingposteriorly, give rise to the parieto-occipital and calcarinefissures. Like the hippocampal, these fissures produceelevations upon the inner surface of the pallium, thatformed by the parieto-occipital early disappearing, whilethat produced by the calcarine persists to form the calcar( minor) of adult anatomy. The three fissures just described, together with the. Fig. 226.—Brain of an Embryo of the Fourth , Cerebellum; />, pons; s, Sylvian fossa. 424 THE DEVELOPMENT OF THE HUMAN BODY. chorioidal and the fossa of Sylvius, are all formed by thebeginning of the fourth month and all affect the entirethickness of the wall of the hemisphere, and hence havebeen termed the primary or total fissures. Until the begin-ning of the fifth month they are the only fissures present,but at that time secondary fissures, which, with one excep-tion, are merely furrows of the surface of the pallium,make their appearance and continue to form until birthand possibly later. Before considering these, however,certain changes which occur in the neighborhood of theSylvian fossa may be described. The fossa is at first a triangular depression situatedabove the temporal lobe on the surface of the the fourth month it deepens considerably, so thatits upper and lower margins become m
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
